textproduct: Rapid City

KEY MESSAGES

-Cool and unsettled through Friday, warming up after

-Good chance of showers Thur into Fri as an upper trough moves through the region

UPDATE

Issued at 950 PM MDT Tue May 19 2026

Departing SFC high will support another cool night as clear skies work with light winds and dry air in place. Frost is not expected to be very widespread tonight outside of northeast WY, being mainly confined to low lying areas and valleys. Upper trough will move east across the Rockies Wed, with the lee-side trough pushing into the FA. Increasing LL moisture per SE flow and an impulse to the south will be enough to support a few isolated showers and TS across mainly western SD in the afternoon. Broad brushed 20 pops across most of that area, with slightly higher numbers over the northern Black Hills. Main upper trough will move into the region Thur with the stalled sfc trough running N-S across the FA, INVOF of the SD/WY line. Conditional instability combined with height falls and sufficient moisture will allow for diurnal convection, initiating along the trough and the Black Hills. Convection will likely wane Thur night with additional showers Friday as the upper trough moves over the region and diurnal heating occurs. Adjusted pops accordingly. Otherwise, warmer and drier weather is on track this weekend into early next week.

DISCUSSION

(This Evening Through Tuesday) Issued at 125 PM MDT Tue May 19 2026

Current upper air models show the upper trough axis east of the forecast area this afternoon, with west northwest flow over the region. 19Z surface analysis depicts high pressure over Wyoming, weak surface trough over central MT. Satellite shows widespread CU across the forecast area, with little vertical extent. Temperatures currently sit in the 40s to mid 50s with light winds predominantly out of the northwest.

Brief shortwave ridge settles in Wednesday into Thursday, prompting a slow warming trend with mostly dry conditions. Weak surface trough in MT passes through Wednesday. This forcing may spark some isolated to showers/storms but no significant QPF is expected through the first half of Thursday. As ridge shifts eastward, troughing once again slides across the Rockies and into the northern and central plains. Synoptic forcing will prompt widespread precipitation the latter half of Thursday into Friday. Current NBM probabilities for precip >= 0.25" has a wide swath of 60 to 80 percent over most of western SD, excluding far northwestern SD. Based off the current track of this system, highest QPF amounts are expected in the Black Hills and southwestern SD

Precipitation is expected to taper off from west to east later Friday, and upper ridge slowly builds over the weekend. Expect highs to jump into the 70s and 80s by Saturday, and stick around through the forecast period.

AVIATION

(For the 06Z TAFS Through 06Z Wednesday Night) Issued At 1009 PM MDT Tue May 19 2026

VFR conditions expected through most the forecast period. The exception will be south central SD Wed. MVFR cigs will move into the area there as an impulse skirts the region Wed morning. Otherwise, isolated shra/ts are possible Wed afternoon across western SD.

UNR WATCHES/WARNINGS/ADVISORIES

SD...Frost Advisory until 8 AM MDT /9 AM CDT/ Wednesday for SDZ002- 012>014-027-030>032-041>044-046-047-049-073-075>078. WY...Freeze Warning from 2 AM to 8 AM MDT Wednesday for WYZ055-056- 058>060.